Inorganic nitrate explosive composition coated with hydrazine or guanidine compounds



United States Patent 3,144,367 1N ORGANIC NITRATE EXPLOSIVE COMPOSITION COATED WITH HYDRAZINE OR GUANIDINE COMPOUNDS Bertil Petrus Enoksson, Gyttorp, Sweden, assignor to Nitroglycerin Aktiebolaget, Gyttorp, Sweden, a company of Sweden No Drawing. Filed Mar. 6, 1962, Ser. No. 177,723 Ciaims priority, application Germany Mar. 7, 1961 11 Claims. (Cl. 149-8) INTRODUCTION This invention generally relates to novel blasting explosives and propellant compositions containing inorganic nitrates. More particularly, this invention relates to novel ammonium nitrate explosive compositions having improved properties.

BACKGROUND Many pulverous and plastic explosives and propellants contain ammonium nitrate and other inorganic nitrates. Ammonium nitrate has the tendency to absorb moisture and to cake. Explosive compositions containing a substantial amount of ammonium nitrate therefore often harden on storing and become difficult to handle, e.g. when a detonator is inserted into the cartridge and on loading the borehole. This tendency also causes difficulties in manufacturing the explosive and when handling in the blasting area.

Earlier it is known how to reduce said tendency of ammonium nitrate for explosive purposes by coating the crystals with wax, TNT or paraifin or by addition of pulverous substances such as Wood flour which keep the salt particles separated, but a satisfactory protection against caking was not achieved. Such additions to ammonium nitrate also restrict the range of compositions to be used in preparing the explosives.

OBJECTS It is therefore an object of this invention to produce an improved ammonium nitrate type of explosive and propellant having better storage properties and a higher density.

Further objects and other advantages of the invention will be more apparent after reading the following detailed description and examples.

THE INVENTION The present invention relates to explosives and propellants which contain Or are prepared from an inorganic crystalline nitrate coated with certain compounds comprising a basic nitrogen containing group and at least one hydrofobic group. It was now found that certain guanidine and hydrazine derivatives with at least one hydrofobic group e.g. a hydrocarbon chain having at least 8 carbon atoms are particularly effective to prevent the caking of ammonium nitrate. The number of carbon atoms in the hydrocarbon chain is preferably 12-20 e.g. a dodecyl, hexadecyl or octadecyl chain.

THE AMMONIUM NITRATE The ammonium nitrate used in accordance with this invention may consist of any type of ammonium nitrate which has been heretofore used for the manufacture of explosives. As those skilled in the explosives art will appreciate, this comprises ammonium nitrate of a wide range of particle sizes, density, water content, etc. The exact properties of the ammonium nitrate are not critical to the present invention.

The best result is obtained when the crystallized ammonium nitrate is coated with the agent at a temperature 3,144,367 Eatented Aug. H, 1964 higher than the melting point of the agent and then the salt is permitted to cool under stirring. It is possible to add the agent to a smaller part of the ammonium nitrate and then admix said portion with the bulk of the ammonium nitrate. To obtain a satisfactory effect a minimum amount of 1 mg. of the agent has to be added for each g. of ammonium nitrate. Higher amounts than, 0.5 g. for each 100 g. of ammonium nitrate may be used but the eifect will not be further improved.

OTHER INGREDIENTS The ammonium nitrate explosive made in accordance with the invention may also contain other ingredients, such as sensitizers, carbonaceous fuels and finely divided combustible metal powders. Examples of a sensitizer would be explosive nitric esters, such as nitroglycerine and nitroglycol, and nitrocompounds, such as trinitrotoluene. Examples of carbonaceous fuels would be coal and wood flour. The finely divided combustible metal powder may be powdered aluminium, silicon or ferrosilicon.

Ammonium nitrate prepared according to the invention will facilitate the preparation of pulverous ammonium nitrate explosives and the explosive will be of higher density and remain freeflowing. The tendency to absorb water and to cake will be considerably decreased. The explosive will be easier to handle and the storage properties are improved. It is also possible to fill the full diameter of the borehole and hence the blasting is improved.

Plastic ammonium nitrate explosives are composed of crystallized ammonium nitrate suspended in a liquid, a viscous solution or a gel phase. To take care of the oxygen liberated from the ammonium nitrate at the detonation, various combustible componets are added, e.g. wood flour, aluminum, nitrohydrocarbons. The medium in which the ammonium nitrate is suspended is generally an explosive mixture, e.g. cellulose nitrate (l2.0-12.6% N) dissolved in glycerine trinitrate and ethylene glycol dinitrate, but can also be a non-explosive mixture, e.g. cellulose nitrate dissolved in nitrobenzene. When the composition of the mixture causes a rapid combustion but no detonation a propellant is obtained. The ammonium nitrate can be entirely or partly replaced by other oxygen containing compounds e.g. sodium. nitrate.

In manufacturing plastic ammonium nitrate compositions the components are kneaded together. The product can be used directly but is mostly extruded through an orifice and provided with a wrapper or introduced into a suitable container. The coating of the ammonium nitrate with the agent prior to the distribution in the viscous phase of the explosive makes the ammonium nitrate easier to handle and to distribute evenly.

Using the agents of the invention the manufacture of plastic explosives is much facilitated. The plastic viscosity and the yield stress of the compositions are reduced. Thus less power is required for the kneading operation and the extrusion is possible at a lower pressure or at a greater velocity. The maximum amount of solid ingredients in the compositions can also be increased.

The invention will be further described in the following examples of which all percentages are by weight.

Example 1 100 g. of crystallized ammonium nitrate was mixed at 100 C. with 0.1 g. of monooctadecylhydrazine. When the temperature of the salt had fallen to 25 C. 6 g. of nitroglycol, 4 g. of wood flour and 4 g. of aluminum powder were added. The pulverous explosive had good storage properties. The free flowing and the explosive properties were unchanged after a storage of six months.

Example 2 A number of specimens of 100 g. of crystallized ammonium nitrate were prepared. To these specimens but one 0.05 g. of an agent listed in the table below were added. Dynamite compositions of the following recipe were prepared from the various ammonium nitrate specimens.

Percent Ammonium nitrate 61.7 Cellulose nitrate 1.3

Glycerine trinitratezethylene glycoldinitrate (1: 1) 32.5

Trinitrotoluene 0.9 Mononitrotoluene 3 .5 Calciumcarbonate 0.1

The extrudability of the compositions was determined in a laboratory extruder at a rate of shear of 2.3 sec. and the shear stress determined is listed in the following table:

Added agent Shear stress,

dyIL/em. X 10 12 Dioctadeeylhydrazine. 9. Ootadecylhydrazide. 5. 5 0ctadecylguanidine 4. 1 Octadeeylcarbamylgua 8. 7 Oetadecylamide 12 Example 3 100 g. of dynamite compositions defined in Example 2 were admixed with 4 g. of mononitrotoluene and thoroughly kneaded. The extrudability of the dynamite was determined at a rate of shear of 2.3 sec. and the shear stress determined was listed in the following table:

The explosives containing the coated ammonium nitrate had improved storage properties compared with compositions containing non-treated ammonium nitrate.

What is claimed is:

1. A novel explosive and propellant composition comprising particles of an inorganic nitrate, said nitrate particles having a surface coating of a compound selected from the group consisting of a substituted guanidine and hydrazine compound having at least one hydrophobic substituent having between 8 and 20 carbon atoms.

2. An explosive according to claim 1 wherein said nitrate is ammonium nitrate.

3. A novel explosive and propellant composition according to claim 2, wherein the said compound forming the surface coating is present in an amount of 0.001-05 g. for each g. of ammonium nitrate.

4. In known explosive or propellant compositions containing particles of ammonium nitrate, the improvement which comprises a surface coating on said particles of ammonium nitrate, said surface coating consisting of monoctadecylhydrazine.

5. In known explosive or propellant compositions containing particles of ammonium nitrate, the improvement which comprises a surface coating on said particles of ammonium nitrate, said surface coating consisting of dioctadecylhydrazine.

6. In known explosive or propellant compositions containing particles of ammonium nitrate, the improvement which comprises a surface coating on said particles of ammonium nitrate, said surface coating consisting of octadecylhydrazide.

7. In known explosive or propellant compositions containing particles of ammonium nitrate, the improvement which comprises a surface coating on said particles of ammonium nitrate, said surface coating consisting of N,N'-bisally1thiocarbamylhydrazine.

8. In known explosive or propellant compositions containing particles of ammonium nitrate, the improvement which comprises a surface coating on said particles of ammonium nitrate, said surface coating consisting of 3- hydroxy-Z-naphthhydrazine.

9. In known explosive or propellant compositions containing particles of ammonium nitrate, the improvement which comprises a surface coating on said particles, of ammonium nitrate, said surface coating consisting of octadecylguanidine.

10. In known explosive or propellant compositions containing particles of ammonium nitrate, the improvement which comprises a surface coating on said particles of ammonium nitrate, said surface coating consisting of octadecylcarbamylguanidine.

11. Method of preparing explosives and propellants, which comprises coating crystallized ammonium nitrate with a compound selected from the group consisting of a substituted guanidine and hydrazine compound having at least one hydrophobic substituent having between 8 and 20 carbon atoms. 

1. A NOVEL EXPLOSIVE AND PROPELLANT COMPOSITION COMPRISING PARTICLES OF AN INORGANIC NITRATE, SAID NITRATE PARTICLES HAVING A SURFACE COATING OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF A SUBSTITUTED GUANIDINE AND HYDRAZINE COMPOUND HAVING AT LEAST ONE HYDROPHOBIC SUBSTITUENT HAVING BETWEEN 8 AND 20 CARBON ATOMS. 